Maybe this is a simple thing or beginner's mistake... Thanks for your help:

I got a new external backup device with two HDDs in RAID 1 for a secure data backup (Fantec QB-X2US3R). I got this exact device because the manual states very very clearly that a single RAID 1-disk can be accessed also on its own when taken out of the Fantec housing (e.g. when the Fantec goes to the devil)... Now I want to try that scenario before transferring all my data...

The Fantec shows up in LinuxMint correctly, I formatted the RAID 1-disk via LinuxMint's Disks utility with Ext4. It shows correctly as single 4 TB drive (I've got two mirrored 4 TB HDDs in the case)... Everything seems very fine and simple!

Now, when I try to take out one of the HDDs and plug it directly to the computer via a SATA/USB-connector (which I used several times in the past to backup or restore data from all kinds of drives), the HDD shows up in LinuxMint as 1,8 TB drive with Ext4 and I am not able to mount it, error/popup (translated): "Mounting of driveName not possible: Error mounting /dev/sdc at /media/al/driveName: wrong fs type, bad option, bad superblock on /dev/sdc, missing codepage or helper program, or other error"

So why only 1,8 TB (instead of 4) and how can I mount it, when connected directly to the computer?

Best regards and thanks a lot for your big help
al
[LM 19.1 64bit Cinnamon]

Last edited by alLa on Sat Jan 12, 2019 11:52 am, edited 1 time in total.

I think we can keep this thread for reference - maybe someone can use it sometime...?

Conclusion: The oldish SATA/USB converter was indeed to old for the new 4 TB harddrive... Accessing it directly via SATA works like a charm, so I am glad to report that it is possible to take one HDD out of the Fantec QB-X2US3R RAID case (when used in RAID 1) and access it directly (e.g. in case something breaks)...